Effect of Geometric Parameters of Superhydrophobic Surface on Liquid Slip

In this paper, we experimentally study how geometric parameters of textured hydrophobic surfaces affect a liquid slip, empowered by a custom-tuned microfabrication procedure that produces regular micro-patterns of posts and grates on an entire 4” wafer with a good size uniformity and no defect. A pitch of the patterns and a gas fraction of the structured surface are independently controlled, and the slip length over each type of patterns is measured using a rheometer system. On both grates and posts, the slip length increases linearly with a pitch but exponentially with a gas fraction. The trend of exponential increase by gas fraction appears more pronounced on posts than on grates. The defect-free surfaces allow the flows to maintain a de-wetted (Cassie) state at much higher pitches and gas fractions than previously possible, permitting flows with the maximum slip effect.